An atom consist of electron, protons and neutrons. Protons and neutrons are present with in nucleus while the electrons are present out side the nucleus.
All these three subatomic particles construct an atom. A neutral atom have equal number of proton and electron. In other words we can say that negative and positive charges are equal in magnitude and cancel the each other. For example if neutral atom has 6 protons than it must have 6 electrons. The sum of neutrons and protons is the mass number of an atom while the number of protons are number of electrons is the atomic number of an atom.
This diagram show that there are 9 electrons and 9 protons are present. We know that the number of protons or electrons are atomic number of that element. From periodic table we know that atomic number of fluorine is 9 thus the given atom present fluorine atom.
